Cadmium Uptake, In Vivo Metastasis and Subcellular Environmental Response of Five Wetland Plants Using DFT Method

Abstract

The main purpose of this study is to analyze whether Cd²⁺ affects the absorption of Ca²⁺ and Fe²⁺ by the roots of five wetland plants and the toxic mechanism of cadmium on the subcellular structure. Five wetland plant samples were collected from the constructed wetland in the upper reaches of the Yangtze River. Based on the experiment and density function theory (DFT), we measured the Cd²⁺ content in the root, stem, and leaf, the morphological dimensions of plants, and in the subcellular structure the electronic activity of Cd compound was calculated to describe the stability and activity of the products. In general, Zephyranthes candida,Cynodon dactylon, Arundo donax, and Pontederia cordata have distinct cadmium uptake characteristics, while Phragmites communis does not. The results indicated tolerance to cadmium in all but Phragmites communis, which was due to cadmium distribution through the process of transpiration and a mechanical interception. The simulation results showed that Cd²⁺ imposed no obvious inhibition on the absorption of Ca²⁺ and Fe²⁺ in plants, as the energy barrier of the process is about 1–3 eV. Cd²⁺ could improve the amount of pyruvate and glucose by 30% via spd orbital hybridization, making them more chemically reactive. At the same time, Cd²⁺ could replace Mg²⁺ in chlorophyll through a copper substitution reaction, making the electron energy of chlorophyll more concentrated. As a result, the valence-band electron at −40 eV was vacant. In conclusion, we determined that Cd²⁺ has no obvious inhibitory effect on Ca²⁺ and Fe²⁺ in root absorption and that Cd²⁺ could affect the properties of compounds of the subcellular structure and thus produce physiological toxicity.